1. Field of the Invention
The invention relates to a picture display device suitable for receiving a video signal comprising picture information, line and field, synchronizing signals and line and field blanking signals, and for displaying the picture information on a display screen, said device including a generator for generating a periodical staircase-shaped signal for addressing picture elements of the display screen, said signal varying each time upon the occurrence of a periodical clock pulse from a settable initial value upon the occurrence of a start signal and having a stepwise change which is also settable, and subsequently assuming the initial value again under the influence of a reset signal.
2. Description of Related Art
A picture display device of this type is known from European patent application No. 112416. For generating a staircase-shaped signal for the field deflection in a picture display tube, the staircase generator in this known device includes a capacitor which is charged during the occurrence of line frequency clock pulses and is discharged during the occurrence of field frequency reset pulses. The device comprises means for manually setting both the initial value of the staircase shape, i.e. the level of the first horizontally extended step in the field period, and the height of the vertical steps. If the number of clock pulses, hence the number of steps during the field period, is given, the entire staircase shape and particularly its amplitude is wholly determined.
A drawback of the staircase generator in the known device is that some parts of the generator have properties which are dependent on temperature so that the quality envisaged for the displayed picture is not obtained. This drawback is recognized by the Applicant of the above-mentioned European application in a subsequent application, namely in European patent application No. 123,745 in which an improved circuit arrangement is proposed for reducing the temperature dependence.